U.S. patent application number 09/894686 was filed with the patent office on 2002-02-28 for optical pulse observing device.
Invention is credited to Ohishi, Masahiro, Ohtomo, Fumio.
Application Number | 20020024712 09/894686 |
Document ID | / |
Family ID | 18698220 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020024712 |
Kind Code |
A1 |
Ohtomo, Fumio ; et
al. |
February 28, 2002 |
Optical pulse observing device
Abstract
An optical pulse observing device enables the clear observation
of indirect laser light of pulse laser light. The optical pulse
observing device to be used by a user for observing pulse
illumination light directly or indirectly, includes an optical
shutter means that operates for alternate opening and closing in
synchronism with periodic pulses of the pulse laser light so as to
open only during the duration of pulses of the pulse laser light to
pass pulse laser light and external light.
Inventors: |
Ohtomo, Fumio; (Tokyo,
JP) ; Ohishi, Masahiro; (Tokyo, JP) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
18698220 |
Appl. No.: |
09/894686 |
Filed: |
June 28, 2001 |
Current U.S.
Class: |
359/264 ;
359/237; 359/240; 359/244 |
Current CPC
Class: |
G02C 7/101 20130101 |
Class at
Publication: |
359/264 ;
359/237; 359/240; 359/244 |
International
Class: |
G02F 001/07; G02F
001/00; G02B 026/00; G02F 001/01; G02F 001/03 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2000 |
JP |
2000-200331 |
Claims
What is claimed is:
1. An optical pulse observing device to be used by a user to
observe pulse illuminating light directly or indirectly, comprising
an optical shutter means that operates for alternate opening and
closing in synchronism with periodic pulses of the pulse
illuminating light so as to open only during duration of pulses of
the pulse illuminating light to pass pulse illuminating light and
external light.
2. An optical pulse observing device to be used by a user to
observe pulse illuminating light directly or indirectly, comprising
an optical shutter means that operates for alternate opening and
closing in asynchronism with periodic pulses of the pulse
illuminating light at a frequency different from that of the
periodic pulses of the pulse illuminating light so as to open to
pass pulse illuminating light and external light.
3. The optical pulse observing device according to claim 1 or 2,
wherein the respective periods of pulses of the pulse laser light
and the optical shutter device are 30 ms or below.
4. The optical pulse observing device according to claim 1 or 2,
wherein a period in which the pulse of the pulse illuminating light
coincides with an open state of the optical shutter means is
repeated at a frequency that makes Bartley effect effective.
5. The optical pulse observing device according to any one of
claims 1 to 4 further comprising a tuning means for tuning period
of an open state of the optical shutter means to that of the pulses
of the pulse illuminating light.
6. The optical pulse observing device according to any one of
claims 1 to 5, wherein the optical pulse observing device is formed
in a shape of a pair of spectacles to be used by a user for
observing the pulse illuminating light indirectly.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an optical pulse observing
device and, more particularly, to an optical pulse observing device
capable of permitting the clear, indirect observation of pulse
laser light.
[0002] A laser beam has been used as a pointer and a level for a
survey instrument because a laser beam expands scarcely and capable
of highly rectilinear propagation. Helium-neon lasers, i.e., atomic
gas lasers that emit a red light of 632.8 nm in wavelength were
used as a light source of laser devices in earlier times. However,
helium-neon lasers need a large oscillator and a high driving
voltage of several thousands volts and are difficult to handle.
[0003] Recently, semiconductor lasers (hereinafter abbreviated to
"LD ") capable of emitting red light similar to that which is
emitted by helium-neon lasers have been developed and helium-neon
lasers have been gradually replaced by LDs. Since LDs are easy to
handle and can be powered by a battery, LDs have become used on
many survey instruments.
[0004] Since laser light is radiant energy, there is a limit to an
output power of a laser to ensure the safety of the eye. The output
power limits for lasers are specified in minute steps for those
that emit continuous laser light and those that emit pulse laser
light. Output powers exceeding a safety limit are classified
strictly.
[0005] Visible lasers generally employed in survey instruments are
included in those of class 2 that are not required to be used under
the control of a safety manager. Upper limit output power for
visible lasers is 1 mW in the class 2. Although a visible laser
included in a rotary laser device is graded class 2, the output of
the visible laser in 0.25 s for which eyes are closed matters
because of the rotation and hence the output power of the visible
laser may be slightly higher.
[0006] However, since the absolute value of the power of the
visible laser is small, it is difficult to recognize the laser
light emitted by the visible laser visually in the sunshine in the
daytime and the distance of visibility is very short. Such a
problem may be solved by intermittent emission of laser light to
utilize the visual sensitivity of eye. Actually, the visual
recognition of the laser light emitted by the visible laser in the
sunshine is very difficult.
[0007] Although the visibility of green laser light brighter than
red laser light is somewhat higher than that of red laser light, it
is still difficult to visually recognize green laser light in the
sunshine. Thus the use of the visible lasers is limited to a guide
beam for interior finish work or tunnels.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide an
optical pulse observing device that enables the clear observation
of indirect light of pulse laser light and is to be used by a
person for observing direct or indirect light of pulse illuminating
light.
[0009] The optical pulse observing device according to the present
invention includes an optical shutter means that operates for
alternate opening and closing in synchronism with the periodic
pulses of pulse illuminating light so as to open only during the
duration of pulses of the pulse illuminating light to pass pulse
illuminating light and external light.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a pulse laser light
observing device in a preferred embodiment according to the present
invention;
[0011] FIG. 2 is a block diagram of assistance in explaining the
electric configuration of the pulse laser light observing device
shown in FIG. 1;
[0012] FIG. 3 is a diagram of assistance in explaining a
synchronous pulse laser light observing device; and
[0013] FIG. 4 is a diagram of assistance in explaining an
asynchronous pulse laser light observing device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Preferred embodiments of the present invention will be
described with reference to the accompanying drawings.
[0015] Principle
[0016] The reason why laser light is visible inside the room and is
invisible in the sunshine will be explained. A laser emits laser
light of a fixed intensity and a large amount of external light is
incident on the eye. Therefore, the laser light will be clearly
visible even in the sunshine as well as inside the room if only the
external light is intercepted.
[0017] If only the external light is intercepted to reduce the same
by half, the amount of light incident on the eye is reduced by
half. The opening of the pupil increases and the visual sensitivity
of the eye increases as the amount of light incident on the eye
decreases. If the intensity of the laser light is kept unchanged in
this state, the laser light can be easily visually recognized in
the sunshine as well as inside the room.
[0018] Although observation of the laser light with intercepting
the external light is possible when the laser is continuously
emitting laser light and the laser light is being passed through a
filter. However an only shaded, monochromatic image is formed for
the eye of a man at that time. Such a condition is dangerous for
actual work
[0019] To avoid such an undesirable condition, the laser emits
pulse laser light and an optical shutter is operated for opening in
synchronism with pulses of the pulse laser light. If pulse laser
light having a duty factor of 50% or below is used and the optical
shutter is opened in synchronism with the pulses of the pulse laser
light, at least half the amount of the external light is
intercepted. When the optical shutter is thus operated, the amount
of light incident on the eye is greater than that of the external
light that is incident on the eye when all the external light is
intercepted and hence the lightness of the visual field does not
decrease so much and the visibility of the pulse laser light
increases. Since the upper limit output of the laser that emits
pulse laser light may be higher than that of the laser that emits
continuous laser light, the pulse laser light of an increased
intensity can enhance the visual recognition of the laser
light.
[0020] Embodiments
[0021] Referring to FIG. 1, a pulse laser light observing device
1000 in a preferred embodiment according to the present invention
is of a spectacles type. The pulse laser light observing device
1000 includes a main unit 1100 having the shape of a pair of
spectacles, and a control unit 1200. The main unit 1100 has a front
frame holding a pair of liquid crystal shutters 1110. A
photodetector 1120 for detecting pulse laser light is placed on the
front frame of the main unit 1100. The control unit 1200 controls
the pair of liquid crystal shutters 1110 of the main unit 1100. The
control unit 1200 can be worn on the user's waist.
[0022] As shown in FIG. 2, the control unit 1200 includes a
controller 1210, a photoelectric circuit 1220, a liquid crystal
driver 1230, a display 1240, an input unit 1250 and an input
terminal 1260 The control unit 1200 is provided with a power
supply, such as a battery.
[0023] The controller 1210 controls the operation of the liquid
crystal driver 1230 on the basis of a signal given thereto by a
photodetector 1120 of the main unit 1100 to operate the liquid
crystal shutters 1110 properly. The controller 1210 includes a CPU
and controls all the operations of the pulse laser light observing
device 1000.
[0024] The photoelectric circuit 1220 amplifies and shapes the
waveform of an electric signal provided by the photodetector 1120.
The liquid crystal driver 1230 drives the liquid crystal shutters
1110 according to a control signal provided by the controller 1210.
The display 1240 displays data entered by operating the input unit
1250 for monitoring and other necessary data. An external device is
able to enter data through the input terminal 1260 into the
controller 1210. The main unit 1100 and the control unit 1200 of
this embodiment are formed separately. Functions of the control
unit 1200 may be incorporated into those of the main unit 1100.
[0025] A control method to be carried out by the control unit 1200
will be described hereinafter.
[0026] Synchronous Operation
[0027] The controller 1210 controls the liquid crystal shutters
1110 so that the liquid crystal shutters 1110 are operated for
opening periodically in synchronism with periodic pulses of the
pulse laser light for a time corresponding to the duration of the
pulses of the pulse laser beam. The user enters data on the period
of the pulses of the pulse laser light, the duration of the pulses
of the pulse laser light and the like by operating the input unit
1250.
[0028] The photodetector 1120 detects the pulse laser light and
gives a pulse laser light detection signal to the controller 1210.
The controller 1210 compares the pulse laser light detection signal
with a signal representing the periodic opening operation of the
liquid crystal shutters 1110 and controls the liquid crystal
shutters 1110 so that the phase of the opening operation of the
liquid crystal shutters 1110 coincides with that of the pulse laser
light and the opening operation of the liquid crystal shutters 1110
is synchronized with the pulses of the pulse laser light.
[0029] The liquid crystal shutters 1110 and the liquid crystal
driver 1230 constitute an optical shutter device, i.e., an optical
shutter means, that operates in synchronism with the pulses of the
pulse laser light to pass the pulse laser light and the external
light only during the duration of the pulses of the pulse laser
light.
[0030] The respective periods of the pulses of the pulse laser
light and the optical shutter device may be 30 ms or below. Ranges
for the period and duration of the pulses of the pulse laser light
may be determined beforehand, and the opening and closing operation
of the liquid crystal shutters 1110 may be controlled so that the
period of open states, the duration of open states and the phase of
the open states of the liquid crystal shutters 1110 coincide
automatically with the period, the duration and the phase of the
pulses of the pulse laser light, respectively. The pulse laser
light observing device 1000 may be provided with a synchronizing
device for automatically synchronizing the opening operation of the
optical shutter device with the pulses of the pulse laser
light.
[0031] Asynchronous Operation
[0032] A control method in case of an asynchronous operation will
be described hereinafter.
[0033] The eye of a man is unable to sense a flicker flickering at
a frequency not lower than 30 Hz approximately and regards such a
flicker as continuous light of a constant intensity. The eye of a
man is able to sense a flicker flickering at a frequency below 30
Hz. A man feels that a flicker has a luminous intensity higher than
that of stationary light having a luminous intensity equal to that
of the flicker. Such a phenomenon is called "Bartley effect". The
present invention uses Bartley effect. The relation of the period
of the pulse of the pulse laser light and duration time of opening
and closing the liquid crystal shutters 1110 in the case of
asynchronous operation is shown in FIG. 4.
[0034] Pulse laser light has pulses as shown in FIG. 4(a) and the
liquid crystal shutters 1110 are opened and closed as shown in FIG.
4(b). FIG. 4(c) shows light pulses transmitted by the liquid
crystal shutters 1110 and FIG. 4(d) show a mode of response of the
eye to the pulse laser light transmitted by the liquid crystal
shutters 1110.
[0035] The period of pulses of the pulse laser light is 30 ms or
below. The liquid crystal shutters 1110 are opened and closed in
timing slightly different from that of the pulses of the pulse
laser light. As shown in FIG. 4, pulses of the pulse laser light
coincide with the open state of the liquid crystal shutters 1110
for 50 ms and do not coincide with the open state of the liquid
crystal shutters 1110 for the next 50 ms. Thus, the coincidence of
the pulses of the pulse laser light and the open state of the
liquid crystal shutters 1110 occurs at intervals of 100 ms.
[0036] The liquid crystal shutters 1110 transmit pulses of the
pulse laser light emitted while the liquid crystal shutters 1110
are open and those emitted while the liquid crystal shutters are
closed are not transmitted.
[0037] FIG. 4(d) show a mode of response of the eye to the pulse
laser light transmitted by the liquid crystal shutters 1110 Since
the eye of a man does not respond to a light pulse having a pulse
width of 30 ms or below. Therefore, the observer feels that a light
pulse having a pulse width of 50 ms is repeated at a period of 100
ms as low frequency flickering.
[0038] On the other hand external light has a constant intensity
and hence has no relation with synchronism between the opening
operation of the liquid crystal shutters 1110 and the pulses of the
pulse laser light. The liquid crystal shutters 1110 transmit
external light only while the liquid crystal shutters 1110 are in
an open state. Since the external light is interrupted at a
frequency of 30 Hz or above, the eye is unable to sense the flicker
of external light. Thus, the eye receives external light of a
certain intensity reduced according to the duty factor of the
liquid crystal shutters 1110.
[0039] Thus, the pulse laser light flickering at 10 Hz that makes
Bartley effect effective can be clearly recognized for the external
light reduced to the certain intensity.
[0040] In the second embodiment, only the frequency and duration of
opening of the liquid crystal shutters 1110 are adjusted to those
of the pulses of the pulse laser light, respectively, and the phase
of the opening operation of the liquid crystal shutters 1110 does
not need to coincide with that of the pulse laser beam, which
simplifies the circuit configuration of the control unit 1200.
[0041] The period of pulses of the pulse laser light, the time for
which the open state of the liquid crystal shutters 1110 coincides
with the pulses of the pulse laser light and the frequency of the
period of coincidence are not limited to those shown in FIG. 4 and
may be changed properly provided that the same effect can be
expected.
[0042] Changing the frequency of operation of the liquid crystal
shutters 1110 can change the period of flicker that can be sensed
by the eye. The user is able to enter a desired frequency of the
opening operation of the liquid crystal shutters 1110 for
adjustment by operating the input unit 1250.
[0043] When the frequency of the pulses of the pulse laser light is
known and the period of flicker is fixed, the opening frequency and
the period of opening and closing operation of the liquid crystal
shutters 1110 can be fixed and hence any adjusting operation is not
necessary. The liquid crystal shutters 1110 and the liquid crystal
driver 1230 constitute an optical shutter device, i.e., an optical
shutter means, that operates asynchronously with the pulses of the
pulse laser light to pass the pulse laser light and the external
light only during the duration of the pulses of the pulse laser
light. The pulse laser light is the illuminating light.
[0044] As apparent from the foregoing description, the optical
pulse observing device to be used by a user for observing the pulse
illumination light directly or indirectly according to the present
invention includes the optical shutter means that operates for
alternate opening and closing in synchronism with the periodic
pulses of pulse illuminating light so as to open only during the
duration of pulses of the pulse illuminating light to pass pulse
illuminating light and external light. Therefore, the device has
excellent effect that the pulse laser light can be clearly
recognized even in a light place.
* * * * *